FIG. 1 shows a schematized block diagram of an internal combustion engine 10 known from the prior art, the internal combustion engine 10 known in practice comprising a crankcase 11, which accommodates cylinders (not shown in detail) of the internal combustion engine 10. The cylinders of the internal combustion engine 10 form two cylinder groups 12, 13, and there is a cylinder head housing 14 and 15, respectively, for each cylinder group 12, 13. Interacting with each cylinder group 12, 13 of the internal combustion engine 10 there is an exhaust turbocharger 16 and 17, respectively, and of the two exhaust turbochargers 16 and 17 the figure shows a turbine 18 and 19, respectively, for expansion of an exhaust gas flow from the internal combustion engine and a compressor 20 and 21, respectively, for compression of a combustion air flow to be fed to the cylinders of the internal combustion engine. The combustion air compressed by the compressors 20, 21 of the exhaust turbochargers 16, 17 can be fed to the cylinders or cylinder groups 12 and 13, respectively, of the internal combustion engine 10 via a throttle valve 22 and a so-called pressure system 23.
As can be seen from FIG. 1, combustion air which is to be compressed in the compressors 20 and 21 of the exhaust turbochargers 16 and 17, respectively, is passed via an air filter 24 and 25, respectively, before being fed to the respective compressor 20 and 21, a measuring device 26 and 27, respectively, for the metrological detection of the air quantity fed to the respective compressor 20 and 21 is inserted between the air filters 24 and 25 and the compressors 20 and 21 of the exhaust turbochargers 16 and 17, respectively.
The internal combustion engine 10 known from the prior art and shown in schematic form by means of a block diagram in FIG. 1 furthermore has an open oil circuit with an oil pump 28, only the suction stage of the oil pump 28 being shown, it being possible to use the illustrated suction stage of the oil pump 28 to suck in engine oil and pump it in the direction of the cylinder groups 12 and 13 and hence in the direction of the cylinder head housings 14 and 15, respectively, in order to lubricate the cylinders of the two cylinder groups 12 and 13.
According to FIG. 1, the exhaust turbochargers 16, 17 are coupled to the open oil circuit of the internal combustion engine 10 in such a way that engine oil can be fed to each exhaust turbocharger 16 and 17, respectively, via an inlet line 29 and 30, respectively, from the respective cylinder head housings 14 and 15 in order to lubricate bearings of the respective exhaust turbochargers 16 and 17, after which the engine oil is sucked in the direction of an oil sump 35, namely by the suction stage of the oil pump 28, from the bearings of the respective exhaust turbochargers 16 and 17 via an outlet line 31 and 32, respectively.
The oil pump 28 used or the suction stage thereof is an unregulated constant delivery pump, which has a constant displacement for each revolution. Since the oil pump 28 is driven in a manner dependent on the speed of the internal combustion engine, the oil volume sucked in by the suction stage of the oil pump 28 increases as the speed of the internal combustion engine increases, and, as a result, an increasing vacuum is formed in the region of the bearings of the exhaust turbochargers 16 and 17 as the speed increases. When the vacuum in the region of the bearings of the exhaust turbochargers 16 and 17 becomes too great, the exhaust turbochargers 16 and 17, respectively, can be damaged. Moreover, an excessive vacuum could lead to a malfunction of the exhaust turbocharger.
In order to counteract this problem, there are bypass lines 33 and 34 in the internal combustion engine 10 known from the prior art and shown in FIG. 1, said bypass lines bringing about pressure equalization between the pressure level in the crankcase 11 or cylinder head housings 14 and 15 and the pressure level in the bearings of the exhaust turbochargers 16 and 17. However, these bypass lines 33 and 34 make the structure of an internal combustion engine relatively complex.
Taking this situation as a starting point, it is the underlying object of the present invention to provide a novel internal combustion engine which is of simpler construction.